Molding is a process by virtue of which a molded article can be formed from molding material by using a molding system. Various molded articles can be formed by using the molding process, such as an injection molding process. One example of a molded article that can be formed, for example, from polyethylene terephthalate (PET) material is a preform that is capable of being subsequently blown into a beverage container, such as, a bottle and the like.
As an illustration, injection molding of PET material involves heating the PET material (ex. PET pellets, PEN powder, PLA, etc.) to a homogeneous molten state and injecting, under pressure, the so-melted PET material into a molding cavity defined, at least in part, by a female cavity piece and a male core piece mounted respectively on a cavity plate and a core plate of a mold. The cavity plate and the core plate are urged together and are held together by clamp force, the clamp force being sufficient to keep the cavity and the core pieces together against the pressure of the injected PET material. The molding cavity has a shape that substantially corresponds to a final cold-state shape of the molded article to be molded. The so-injected PET material is then cooled to a temperature sufficient to enable ejection of the so-formed molded article from the molding cavity. When cooled, the molded article shrinks inside of the molding cavity and, as such, when the cavity and core plates are urged apart, the molded article tends to remain associated with the core piece. Accordingly, by urging the core plate away from the cavity plate, the molded article can be subsequently demolded by ejecting it off the core piece. Ejection structures are known to assist in removing the molded articles from the core halves. Examples of the ejection structures include stripper plates, stripper rings and neck rings, ejector pins, etc.
When dealing with molding a preform that is capable of being subsequently blown into a beverage container, one consideration that needs to be addressed is forming a so-called “neck region”. Typically and as an example, the neck region includes (i) threads (or other suitable structure) for accepting and retaining a closure assembly (ex. a bottle cap), and (ii) an anti-pilferage assembly to cooperate, for example, with the closure assembly to indicate whether the end product (i.e. the beverage container that has been filled with a beverage and shipped to a store) has been tampered with in any way. The neck region may comprise other additional elements used for various purposes, for example, to cooperate with parts of the molding system (ex. a support ledge, etc.). As is appreciated in the art, the neck region can not be easily formed by using the cavity and core halves. Traditionally, split mold inserts (sometimes referred to by those skilled in the art as “neck rings”) have been used to form the neck region.
With reference to FIG. 1, a section along a portion of an injection mold 50 illustrates a typical molding insert stack assembly 52 that can be arranged (in use) within a molding machine (not depicted). The description of FIG. 1 that will be presented herein below will be greatly simplified, as it is expected that one skilled in the art will appreciate configuration of other components of the injection mold 50 that will not be discussed in the following description
The molding insert stack assembly 52 includes a split mold insert pair 54 that together with a mold cavity insert 56, a gate insert 58 and a core insert 60 defines a molding cavity 62. Molding material can be injected into the molding cavity 62 from a source of molding material (not depicted) via a receptacle (not separately numbered) in the gate insert 58 to form a molded article. In order to facilitate forming of the neck region of the molded article and subsequent removal of the molded article therefrom, the split mold insert pair 54 comprises a pair of complementary split mold inserts (not separately numbered) that are mounted on adjacent slides of a slide pair (not depicted). The slide pair is slidably mounted on a top surface of a stripper plate (not depicted). As commonly known, and as, for example, generally described in U.S. Pat. No. 6,799,962 to Mai et al (granted on Oct. 5, 2004), the stripper plate is configured to be movable relative to the cavity insert 56 and the core insert 60, when the mold in arranged in an open configuration, whereby the slide pair, and the complementary split mold inserts mounted thereon, can be laterally driven, via a cam arrangement (not shown) or any other suitable known means, for the release of the molded article from the molding cavity 62.
A typical neck ring insert has a body that includes a pair of projecting portions 66 that extend from a top and a bottom face of a flange portion 68. As is shown in FIG. 1, the pair of projecting portions 66 include two male tapers—a top projecting portion 66a and a bottom projecting portion 66b. This type of an arrangement is commonly known in the art as a “core lock type split mold inserts”. In an alternative prior art configuration, it has been known to arrange the top projecting portion 66a as a male taper and to arrange the bottom projecting portion 66b as a female taper. This type of an arrangement is commonly known in the art as a “cavity lock type split mold inserts”. In either case, within a typical prior art implementation, the pair of projecting portions 66 serves a dual function—an alignment function and a locking function (i.e. preventing lateral movement of the neck rings under injection pressure).